At present, driver assistance technologies, including adaptive cruise control (ACC), for providing various types of driver assistance are used in practical applications. A driver assistance apparatus is used to implement a system in which a radar and external sensors, mainly used for camera image recognition, are mounted on a vehicle to recognize and decide a situation around a vehicle; according to the situation, an alarm or a notification is given to the driver to promote the driver to decrease the velocity or stop the vehicle, and driver assistance for the vehicle is controlled. Navigation apparatuses are also mounted in many recent vehicles.
The present invention addresses driver assistance control as main technology in which external sensors, which are typified by cameras, are used to recognize particular objects (such as stop lines, crossing lines, and other markers on roads), calculates a distance up to the object, and control driver assistance so as to make the vehicle velocity at the point of the feature approach a target velocity. In control based on peripheral recognition by camera image recognition, a distance up to which recognition is possible is as short as tens of meters, so the correct distance cannot be recognized until the vehicle approaches the object. When information provided by a navigation apparatus is used, the distance from the driving position of the vehicle to a target point can be obtained even when the target point is far from the vehicle. However, vehicle positions estimated by navigation apparatuses may include large estimation error ranging from several meters to tens of meters; contrary to the use of camera image recognition, the vehicle is easily affected by the estimation error as it approaches the target, and thus correct control cannot be implemented. Accordingly, when large deceleration is required gradually for example, to automatically stop until the target is reached, a switchover as disclosed in Patent Document 1 is preferable. Specifically, driver assistance is controlled by making a switchover as follows: when the target point is far from the vehicle, distance information based on navigation information is used; when the target point is approached, more accurate information provided by external sensors such as cameras or the like is used.
In driver assistance control using external sensors, control based on sensor information must be usually stopped in a situation in which the reliability of the sensor information is substantially lowered. For example, in driver assistance control using a camera image recognition apparatus as disclosed in Patent Document 2, the driver assistance system controller cancels following distance control or constant-velocity driver assistance control according to the weather and road condition because distance detection performance is lowered in falling weather such as rainy weather.
[Patent Document 1] Japanese Patent Laid-open No. 2004-86363
[Patent Document 2] Japanese Patent Laid-open No. Hei 10(1998)-81156